Melt the chocolate in a heatproof bowl over a pan of simmering water until smooth; cool. Beat the egg yolks and sifted icing sugar in a small bowl with an electric mixer until smooth. Whisk in the liqueur, coffee, chocolate, then oil.

Beat the eggwhites in a small bowl with an electric mixer until soft peaks form. Fold egg whites into the chocolate mixture in two batches. Spoon the mixture into eight serving glasses or serving dishes (1/3-cup capacity) then cover and refrigerate until set. Serve topped with strawberries and chocolate curls, if desired.